The sample analyte analysis capabilities of Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) and Microwave Coupled Plasma-Mass Spectrometer (uW-MS) systems and the like, are well established.
For insight, it is noted that (ICP-MS) systems can comprise an Inductively Coupled Plasma (ICP) system followed by a Mass-Spectrometer (MS) system, wherein the (ICP) system is an (ICP) "Torch" with an enclosed space therein in which a plasma is inductively formed by application of high frequency electrical energy, via a coil situated around said enclosed space. An (ICP) Torch, it is mentioned, typically comprises a "Sample Injector Tube" present centrally within various other concentrically surrounding tubes, which various other concentrically surrounding tubes typically project beyond the projecting end of said sample injector tube, thereby providing an enclosed space therewithin, beyond the projecting end of said sample injector tube. Typically, during use, a sample solution is distally nebulized, (ie. atomized into small diameter droplets), and the nebulized droplets are caused to flow through said sample delivery tube into said plasma containing enclosed space. Gas is simultaneously caused to flow through annular space(s) between concentric tubes within said (ICP) Torch with the effect being that nebulized sample is directed into the plasma containing enclosed space in a plume. When a sample component is injected into said plasma containing enclosed space of an (ICP) Torch, electrons therein are excited into high energy atomic orbitals and some are dislodged entirely, thereby providing ionized sample components which are suitable for analysis in a mass-spectrometer system.
Other sample analyte ionization system configurations eliminate the need for an (ICP) Torch and provide for ionization of nebulized sample analyte injected thereinto by functionally equivalent means. For instance, entry stage ionization chambers contained within a Mass-Spectrometer (MS) system are such functionally equivalent means.
It is to be understood that Mass-Spectrometer (MS) systems comprise means for identifying ionized, (charged), sample components, (ie. analytes), based upon their mass and charge, as mediated and evidenced by said ionized charged sample component trajectory in the presence of electric and/or magnetic fields. For instance, which detector, (in an array of detectors oriented so as to intercept charged particles), a charged particle of a certain mass and charge which is caused to move in an electric field, enters, is determined by factors including the strength of the electric field, the particle velocity, charge and mass.
To provide additional insight it is disclosed that known means for nebulizing sample analyte containing sample solution, prior to injection into an (ICP), include Direct Injection Micronebulizer (DIN) systems. Briefly, (DIN) systems are well suited for directly entering small volumes of nebulized sample analyte containing solution into a plasma, and comprise a sample delivery tube centrally present within an essentially elongated tubular space through a "primary body element", such that during use sample analyte containing solution can be caused to eject from an end of said sample delivery tube simultaneous with the ejecting of a gas from an annular space concentrically formed between an outer surface of said sample delivery tube, and an inner surface of the elongated tubular space through said primary body element. Interaction between said ejecting sample analyte containing solution and said ejecting gas causes said sample analyte containing solution to become subjected to shearing forces and thereby nebulized into small droplets. Preferred (DIN) systems produced by CETAC/TRANSGENOMIC Inc. (which is headquartered in Omaha, Neb., and which is the Assignee for all Wiederin and Zhu Patents cited herein), typically include means for adjusting the positioning of an end of a sample delivery tube with respect to the end of the concentrically surrounding primary body element. Said positioning, it is noted, is often critical to successful nebulization of entered sample analyte containing solution.
Additional known systems for nebulizing sample analyte containing sample solution are known as Micro-Concentric Nebulizer Systems, (eg. MCN systems), and while (MCN) systems are generally functionally similar to (DIN) systems, (MCN's) are often simpler in that they comprise a primary body element with provision for simultaneous entry of both sample analyte containing sample solution and a flow of gas, and with provision for securing to a Spray Chamber which is sequentially present prior to a an Inductively Coupled Plasma (ICP) or Mass-Spectrometer (MS) system. That is, (MCN) systems need not be of a shape and size such that they can be easily inserted into an (ICP) Torch, and need not provide means for enabling the positioning of a sample solution ejecting end thereof near to an (ICP) in use. Instead, an (MCN) system need provide only means for simultaneous entry of sample analyte containing sample solution and a flow of gas, and means for coupling to a sequentially next stage, (eg. a spray chamber).
A Search of relevant references has identified a Fassel et al. U.S. Pat. No. 4,575,609 which describes a micro-nebulizer which inserts in, and mounts directly to a sample injector tube of a standard (ICP) torch. U.S. Pat. Nos. 5,212,365 and 5,272,308 to Wiederin describe improved (DIN) systems which do not require the presence of an (ICP) Torch sample injector tube as a part of their construction, but rather provide an elongated primary body element with a longitudinally oriented hole therethrough, through which longitudinally oriented hole a centrally located sample delivery tube extends. The Wiederin (DIN) systems allows for easy access to the space inside the Primary Body Element to allow non-destructive cleaning, and allows easy adjustment of the location of the relative positions of the sample ejecting end of the Sample Delivery Tube and the end of the Primary Body Element. Said adjustment allows optimizing the nebulizing ability of the Wiederin (DIN). A Meyer U.S. Pat. No. 4,990,740 describes a low operational pressure (DIN)-like system at a lower aspect thereof, with a series of impactors thereabove. Said impactors serve to deflect large diameter droplets, (over approximately fifteen (15) microns in diameter), away from injection into an upper aspect of said system.
A Chan et al. U.S. Pat. No. 5,233,156 is also known and teaches Torches of the type used in (ICP) systems, which Torches are designed for use with high solids content samples. Standard (ICP) torches are also described therein.
Another known U.S. Pat. No. 5,192,865 to Zhu is also disclosed as it describes entry of a nebulized sample analyte into a (MS) system via an Atmospheric Pressure Afterglow Ionization System. Nebulized sample analyte is injected into said 865 Patent system sequentially after the location of a carrier gas ionization means which serves to produce metastable species in use. In addition, another known Zhu U.S. Pat. No. 5,259,254 is also disclosed as it describes nebulization of a sample analyte containing solution, (by ultrasonic means), in a system which comprises a spray-chamber.
As mentioned, in some applications of sample solution nebulizing systems, it is not necessary to position an end of the sample solution nebulizing system from which nebulized sample solution is caused to exit in use, near a plasma in, for instance, an (ICP) system. The 308 Patent to Wiederin et al. describes such a system wherein is present, (between a (DIN) and a (MS) system), sequentially intervening desolvation and enclosed filter solvent removal systems, the purpose thereof being to remove and dispose of solvent in nebulized sample analyte containing sample solution droplets prior to entry of desolvated nebulized sample analyte to said (MS) system.
Importantly, it has been noted that in certain applications of (DIN) and (MCN) systems, at times sample solution delivery tubes, (ie. tubes which carry sample analyte containing sample solution), become crushed, thereby blocking flow of sample analyte containing solution therethrough. This is especially true where a utility providing thin-walled capillary is utilized as sample delivery tube. It has also been noted that flow of sample analyte containing solution through (DIN) or (MCN) systems can, during use, cause sample analyte containing solution therein to become electrically charged. Discharge of said electrical charge has been noted to induce untoward spikes in (MS) system output, thereby reducing sample analyte analysis capability. In addition, where a (DIN) or (MCN) is secured to a spray chamber means, it has been found that relatively large droplets of nebulized sample analyte containing solution can condense therein, onto the end of the (DIN) or (MCN) from which exits nebulized sample analyte containing solution in use. This can interrupt smooth flow of nebulized sample analyte containing solution, and can result in an undesirable effective "re-nebulization" of said condensed sample analyte containing solution, by gas exiting the (DIN) or (MCN). This effect is undesirable as it complicates interpretation of results provided by use of a (MS) system into which resulting nebulized sample solution is entered. It is also noted that systems for nebulizing, and analyzing, analytes in sample analyte containing solutions which have crevasses therein are prone to sample analyte carry-over "memory effects", wherein sample analyte entered during one analysis procedure is retained and undesirably released during a subsequent sample analysis procedure. Said "memory effect" is undesirable as it can lead to erroneous indication of the presence of a sample analyte in a specific sample analyte containing solution in which it is not actually present.
It should then be appreciated that even in view of the identified known art, need remains for convenient-to-use systems which include a relatively physically simple, (eg. MCN), system for subjecting a sample analyte containing solution to a nebulization procedure, followed by injection of the results into an (ICP), or functionally equivalent sample analyte ionization system, wherein ionization of sample analyte analytes occurs in use, so that a sequentially following (MS) system can be applied to the detection, and analysis, of sample analyte(s) present therein. Said relatively simple system for subjecting a sample analyte containing solution to a nebulization procedure, should provide for use with spray-chamber and/or desolvation means and/or solvent removal means, between it and a sample analysis system such as an (MS) system without introducing identified difficulties associated with sample delivery tube kinking and/or crushing at points of securement to said sample analyte containing solution nebulizing means, electrostatic spike development, the occurrence of sample solution "re-nebulization" and sample analyte memory effects, in addition to providing function enhancing interface system means for interconnecting said relatively simple system for subjecting a sample analyte containing solution to a nebulization procedure, to a spray-chamber and/or desolvation means and/or solvent removal system means.